The present invention relates to information recording media, and particularly to a high-density information recording medium and a high-density optical recording medium of which the track width is smaller than a beam spot or a detecting means such as a magnetic head.
Japanese laid-open patent publication No. 6-176404, for example, describes an example of a high-density (narrow track) recording medium. This example uses as a recording medium an optical recording medium in which groove portions and land portions are formed on a substrate and information recording areas are formed on both of the groove portions and the land portions. Prepits are formed on a virtual prolonged line of a boundary portion between the groove portion and the land portion as identification information of a recording unit (sector), whereby recording information is recorded on both of the groove portions and the land portions and identification (address) information indicative of a recording area is handled by the prepits. Also, one prepit commonly uses address information for a pair of groove portion and land portion. According to this system, when the recording medium of this system is applied to a phase change type recording medium and a magneto-optical recording medium, information from the adjacent land portion or groove portion can be prevented from being mixed into the groove portion and the land portion owing to an interference effect caused within the beam spot (i.e. crosstalk can be cancelled out), and hence the tracks of the recording medium can be narrowed, thereby making a high-density recording become possible.
However, in the example according to the related art, inasmuch as information indicative of the position on the information recording medium is concentrated in the prepit portions and the prepit portions located in a discrete fashion, position information cannot be obtained from portions other than the prepit portions. As a consequence, it is difficult to control a rotational speed of a disk precisely with a high reliability. There is then presented the problem from a reliability standpoint that the recording medium according to the relate art is not persistent to, in particular, defects or the like.
A first object of the present invention is to provide an information recording medium in which the aforementioned problems can be solved and which can be made high in recording density and highly reliable by assigning position information to other portions than prepit portions.
A second object of the present invention is to provide an information recording and/or reproducing method in which the aforementioned problems can be solved and in which information can be recorded and/or reproduced with a high recording density and with a high reliability by using an information recording medium in which position information is assigned to other portions than prepits.
In order to attain the above-mentioned first object, the present invention used the means which follow:
(1) In an information recording medium having almost spiral-like or concentric tracks comprising both of groove portions and a land portion between the groove portions, the recording medium is divided into groups of a plurality of areas in the radius direction, each track is divided at circular arc recording units having the same central angle arranged to be radial in the radius direction within each group, identification information indicative of the recording unit is provided in the track at every recording unit, the each track is divided into groups such that a length of a circular arc-shaped recording unit becomes almost constant between the groups, and the groove portion and the land portion are wobbled in the radius direction of the information recording medium.
Thus, position information can be reliably obtained in the recording portions because the identification information is provided at every recording unit, and the groove portions and the land portions, which are the recording portions, are wobbled. In other words, recorded information can be accessed reliably and recording information can be positioned with a high accuracy. Further, since the recording units are arranged tb be positioned in the radius direction of the information recording medium, the tracks can be accessed with ease, and a crosstalk caused between position information of each recording unit can be suppressed to the minimum. Since the tracks are disposed in such a manner that the lengths of the circular arc-shaped portions which are the recording units become almost the same, the recording density becomes approximately uniform. Thus, it becomes possible to efficiently use the whole surface of the disk. Furthermore, it is possible to correct the displacement of tracking with a high accuracy.
Japanese laid-open patent publication No. 6-243468 describes a technology in which grooves are wobbled and a linear velocity of a disk is calculated by a wobble cycle detecting circuit, thereby rotating the disk at a constant linear velocity (CLV).
(2) Wobble cycles and phases of the groove portion and the land portion are uniformly arranged to be radial with respect to the adjacent tracks within each group, whereby the wobbling between the adjacent tracks can be reliably reproduced without interference. Also, since the widths of the respective tracks become constant, the recording characteristics can be prevented from being affected.
(3) A constant integral multiple of the cycle at which the groove portion and the land portion are wobbled is made coincident with the length of the circular arc-shaped recording unit. Thus, the starting point and the ending point of the recording unit can be detected reliably, and it becomes possible to detect an accurate position in the recording unit. Moreover, since the length of the recording unit and the wobble cycle in which the groove portion and the land portion are wobbled are synchronized with each other, it is possible to automatically and constantly keep the relative speed of the recording medium constant by making the frequency of the wobbling become constant.
(4) The maximum values of the amplitudes of wobbling in which the groove portion and the land portion are wobbled were selected to be smaller than one-tenth of the track width. Thus, the influence that is exerted upon the recording and reproducing characteristics by the above-mentioned wobbling could be suppressed to be less than 1xe2x88x92cos (180/10)=xe2x88x9226 dB, and the influence which affects an S/N (signal-to-noise ratio)(xcx9c20 dB) necessary for the normal recording and/or reproduction can be suppressed to be negligibly small.
(5) Identification information was formed by prepits which were very small concave portions and convex portions disposed in the spacing between the groove portion and the land portion. Thus, it becomes easy to mass-produce an information recording medium with identification information previously provided therein by a simple manufacturing process such as an injection molding. Therefore, a productivity with which an information recording medium is mass-produced can be raised.
(6) Identification information was disposed in an intermediate portion formed between a track and a track adjoining to the former track. Thus, since one identification information can be used by both of the two tracks, identification information assigned to one information area is doubled, and hence a reliability of the identification information can be improved. The information tracks in which identification information is disposed can be discriminated from each other by effectively utilizing a difference between the positions of the directions along the track. Moreover, since a relationship between the identification information of the adjacent track and the identification information of the track falls within a constant range, it becomes possible to discriminate the track from the identification information of the adjacent track.
(7) The track of the groove portion and the track of the land portion were disposed at least at one portion of the one circumference of the information recording medium in such a way as to be connected from the groove portion to the land portion or from the land portion to the groove portion. Thus, since it becomes possible to continuously access the tracks from the recording track of the groove portion to the recording track of the land portion, an effective transfer rate of information can be raised. Therefore, it becomes easy to record and/or reproduce successive information such as moving picture information on and/or from the information recording medium.
The present invention used the following means in order to attain the above-mentioned second object:
(8) The above-mentioned information recording medium was used, and light was irradiated on the track. Then, a wobbling signal was detected by detecting reflected light with at least two split photo detectors, and information was recorded in the information recording medium and/or reproduced from the information recording medium by controlling a rotational speed of the information recording medium in such a manner that the cycle of the detected wobbling signal becomes constant. Thus, a rotational speed of the disk-like information recording medium can be controlled with ease and with a high accuracy in such a manner that a scanning velocity of light on the information recording medium becomes almost constant.
(9) The above-mentioned information recording medium was used, and light was irradiated on the track. Then, a wobbling signal was detected by detecting reflected light with at least two split photo detectors, and information was recorded on the information recording medium by using a clock which was generated in synchronism with the phase of the detected wobbling signal. Thus, since it becomes easy to make the length of each recording unit on the information recording medium become constant, the lengths of extra gaps on the information recording medium can be minimized.
(10) The above-mentioned information recording medium was used, and light was irradiated on the track. Then, a wobbling signal was detected by detecting reflected light with at least two split photo detectors, and a displacement of the track was detected by comparing the amplitudes of the wobbling signals obtained from the two photo detectors of the split photo detector. Thus, since information can be recorded on the information recording medium and/or reproduced from the information recording medium while the displacement amount of the track is being monitored constantly, a reliability in the positioning servo can be improved greatly.
(11) The recording medium is an optical disk of a concentric-shaped or spiral-like groove configuration arranged along the tracks. This groove structure is wobbled in the radius direction of the optical disk. The track of the optical disk is divided into a plurality of recording units by radial boundary lines in the track direction. Of the recording units thus divided by the radial boundary lines, at least two recording units adjoining in the radius direction of the optical disk constitute one zone, and the groove structures included in the respective recording units within one zone have almost the same number of the wobbling.
Thus, since the position information can be highly reliably obtained even from the recording portions owing to the wobbling, recorded information can be accessed reliably. Hence, it becomes possible to accurately position recorded information on the optical disk. Further, since the recording units are arranged to be radial in the radius direction within the group (zone), recorded information among the tracks can be accessed with ease, and a crosstalk between the position information of the respective recording units can be suppressed to the minimum.
The recording unit need not always agree with the length of the sector, and a plurality of sectors of more than two sectors may be collected as the recording unit. Furthermore, a plurality of recording units may be collected as a logical sector or a logical block used to correct an error. At any rate, the recording unit herein will be referred to as an area of almost constant length provided within the optical disk.
(12) The recording medium is an optical disk of a concentric-shaped or spiral-like groove configuration arranged along the tracks. This groove structure is wobbled in the radius direction of the optical disk. The track of the optical disk is divided into a plurality of recording units by radial boundary lines in the track direction. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction of the optical disk constitute one zone. The optical disk includes a plurality of zones, and the groove structures included in one recording units within any zone have almost the same number of the wobbling.
Thus, since the relationship between the information recording unit and the duration of the wobbling becomes equal on the whole surface of the optical disk, it becomes possible to control the rotational speed of the optical disk and to generate the recording clock by using the wobble signal without switching the wobble signal in the zone. Therefore, a density within the optical disk can be made almost uniform by the apparatus of the simple configuration, and hence it becomes easy to utilize the whole surface of the optical disk efficiently.
(13) The recording medium is an optical disk having a concentric-shaped or a spiral-like groove configuration, and the groove structure is wobbled in the radius direction of the optical disk. The groove structure of the optical disk is divided into a plurality of recording units in the circumference direction of the optical disk by the radial boundary lines. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction constitute one zone, and the groove structures which are adjoining to each other in the radius direction of the optical disk have substantially the same wobbling cycle.
Alternatively, there might be used the following means:
(14) The recording medium is an optical disk having a concentric-shaped or a spiral-like groove structure, and the groove structure is wobbled in the radius direction of the optical disk. The groove structure of the optical disk is divided into a plurality of recording units in the circumference direction of the optical disk by the radial boundary lines. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction of the optical disk constitute one zone. The groove structures of the adjacent recording unit areas in the radius direction of the optical disk within one zone have almost the same wobbling cycle and the same number of the wobbling.
Thus, since the position information can be reliably obtained even from the recording portion, recorded information on the optical disk can be accessed highly reliably, and the recorded information can be positioned with a high accuracy. Furthermore, since the wobbling is arranged to be radial in the radius direction within the group (zone) and the phases of the wobbling are the same in the grooves, it becomes easy to access the tracks of the optical disk. Also, it becomes easy to detect the wobbling signal at a high quality of a signal. Strictly speaking from a theory standpoint, although this wobbling signal has a cycle proportional to the position at which the groove is located in the radius direction within one zone, the grooves which are close to each other like the grooves within one zone have almost the same wobbling cycle. Incidentally, the number of the wobbling need not always be limited to an integral number within the recording unit area.
(15) The recording medium is an optical disk having a concentric-shaped or a spiral-like groove structure. The groove structure is wobbled in the radius direction of the optical disk, and the groove structure of the optical disk is divided into a plurality of recording units in the circumference direction of the optical disk by the radial boundary lines. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction constitute one zone. The optical disk includes a plurality of zones, and the groove structure has almost the same wobbling cycle in the unit areas which are adjoining to each other in the radius direction of the optical disk within every zone, and also has the same number of the wobbling.
Thus, since the relationship between the information recording unit and the duration of the wobbling cycle becomes equal on the whole surface of the optical disk, it becomes possible to control the rotational speed of the optical disk and to generate a recording clock by using the wobbling signal without switching the wobbling signal in the zone. Thus, since a density within the optical disk can be made almost uniform by the apparatus of the simple configuration, it becomes easy to utilize the whole surface of the optical disk efficiently.
(16) The recording medium is an optical disk having a concentric-shaped or a spiral-like groove structure. The groove structure is wobbled in the radius direction of the optical disk, and the track of the optical disk is divided into a plurality of recording units in the track direction by the radial boundary lines. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction of the optical disk constitute one zone. Central angles corresponding to one period of the wobbling of the groove structure included in the respective recording units within one zone are the same, and the starting positions of the wobbling are arranged to be radial in the radius direction of the optical disk at each recording unit.
Thus, since the wobbling signal between the adjacent tracks can be reliably reproduced without interference and the width of each track becomes constant, the recording characteristics can be protected from being affected.
(17) The recording medium is an optical disk having a concentric-shaped or a spiral-like groove structure. The groove structure is wobbled in the radius direction of the optical disk. The track of the optical disk is divided into a plurality of recording units in the circumference direction of the optical disk by the radial boundary lines. Of the recording units thus divided by the radial boundary lines, at least two recording units which are adjoining to each other in the radius direction constitute one zone. Assuming that N is one integral number that is made common to all of the recording units on the optical disk, then the optical disk includes a plurality of zones, and all wobble cycles included in one recording unit of each zone is set to approximately 1/N times the length of the recording unit.
Thus, since the relationship between the information recording unit and the duration of the wobbling cycle becomes equal on the whole surface of the optical disk, it becomes possible to control the rotational speed of the optical disk and to generate the recording clock by using the wobble signal without switching the wobble signal depending on the zone, and hence a density within the optical disk can be made almost uniform by the apparatus of the simple configuration. As a consequence, it becomes easy to make effective use of the whole surface of the optical disk efficiently. Moreover, since the integral multiple of the wobbling cycle agrees with the length of the recording unit, the phases of the wobbling signal can be perfectly connected between the adjacent recording units without fractions. Hence, it becomes easy to generate a timing signal such as a clock over a consecutive recording unit by using the wobbling signal. The fact that the wobbling signal is connected without fractions as described above means that the phases of the wobbling signals are continuous between the adjacent recording units, and the wobbling signals need not always be continuously connected physically. Specifically, although it is possible to use such a wobble structure that the wobbling signal is dropped out over several cycles at the boundary portion of the recording units, if such dropout portion is interpolated (compensated for), then the phase of the wobble signal is continuously connected in the adjacent recording unit areas.
(18) Identification information was provided at every recording unit. Thus, it becomes easy to access the recording unit on the optical disk. Also, it becomes possible to fix the position of the beam spot at all positions on the optical disk by combining a signal detected from the wobbling and the identification information. Therefore, a reliability with which information is recorded on the optical disk and/or reproduced from the optical disk can be improved. Moreover, an accuracy with which recorded information is positioned on the recording medium can be improved. Thus, a buffer area required when information is recorded on the recording medium can be reduced. As a consequence, it becomes possible to enlarge a recording capacity of the recording medium. Moreover, even when a part of identification information on the optical disk cannot be detected due to a defect or the like, the position of the beam spot can be identified based on beam spot position information obtained from the wobbling so that a reliability with which information is recorded on the optical disk and/or reproduced from the optical disk can be improved greatly. If the above-mentioned advantage is used, even though recording media are not inspected when they are shipped, a reliability with which information is recorded on the optical disk and/or reproduced from the optical disk can be maintained so that a cost of the recording medium can be reduced considerably. Moreover, since the recording medium is very resistant to smudges, and need not be protected by some suitable means such as a case. Thus, it becomes possible to provide an inexpensive recording medium.
(19) The above-mentioned identification information was formed by prepits comprising optical concave or convex portions.
Thus, optical disks can be mass-produced with ease by a replica method, and it becomes possible to provide stable and highly-reliable identification information which can be prevented from being deteriorated.
(20) The recording medium includes information recording areas provided along the central line of the groove structure and the central line of the land structure.
Thus, according to the above-mentioned information recording areas, it becomes possible to dispose recorded information with a high density, i.e. it is possible to realize a medium of a high density (large capacity).
(21) Light is irradiated on the recording medium, a wobble signal is detected by detecting reflected light of the irradiated light by a photo detector, and a recording or reproducing timing signal is obtained by using the wobble signal.
Thus, since position information is reliably obtained even from the recording portions by the wobbling of the groove portions and the land portions which are served as the recording portions, recorded information can be accessed highly reliably, and recorded information can be positioned on the recording medium with a high accuracy, i.e. information can be recorded and/or reproduced on and/or from the recording medium highly reliably, and an accuracy with which information is recorded on the recording medium can be raised.
(22) Light is irradiated on the recording medium, and the wobble signal is detected by detecting reflected light of the irradiated light with a photo detector. By using the wobble signal, it is possible to obtain a starting or ending timing at which at least any of recorded information and identification information is recorded on and/or reproduced from the recording medium.
Thus, since timing information can be obtained highly reliably even when a timing at which the recording unit and the identification signal are generated is fluctuated because a revolution rate of the optical disk, for example, is not stable due to the wobbling of the groove portions and the land portions which are served as the recording portions, the recorded information on the optical disk can be accessed highly reliably. As a consequence, a speed at which recorded information is accessed can be raised, and it becomes possible to use an inexpensive motor so that an information recording and/or reproducing apparatus can be produced inexpensively.
(23) At least one identification information is detected by irradiating the recording medium with light. When at least one succeeding identification information which succeeds the identification information is detected, the recording area that should be identified by the succeeding identification information is recorded on or reproduced from the recording medium by using either an identification information detecting signal indicating that the succeeding identification information is detected or a pseudo-succeeding identification information detecting signal which is generated from a recording or reproducing timing signal obtained from the above-mentioned wobbling of the groove portions and the land portions.
Thus, even when the succeeding identification information cannot be detected due to some causes such as defects or smudges, the recording area that should be identified by the succeeding identification information can be accessed by using the signal obtained from the wobbling so that a reliability with which information is recorded on the recording medium and/or reproduced from the recording medium can be increased greatly.
(24) There is provided a method of recording and/or reproducing information in which information is recorded on and/or reproduced from a recording medium by using a timing signal obtained from the wobbling instead of identification information if the identification information cannot be detected when the identification information is detected by irradiating light on the recording medium.
Thus, even when the succeeding identification information cannot be detected due to some causes such as defects or smudges, the recording area can be accessed highly reliably by using the wobble signal, and hence a reliability with which information is recorded on and/or reproduced from the recording medium can be improved greatly. Therefore, since the reliability in recording and/or reproducing information on and/or from the recording medium can be maintained high without inspecting the recording medium when the recording medium is shipped, it becomes possible to reduce the cost of the recording medium considerably. Furthermore, since the recording medium becomes very resistant to the smudges, the recording medium need not be protected by some suitable means such as a case. Therefore, it becomes possible to provide a more inexpensive recording medium.
(25) Light is irradiated on the recording medium, and a wobble signal is detected by detecting reflected light of the irradiated light with a photo detector. When a recording or reproducing timing signal is generated from the wobble signal, at least the portion in which the above-mentioned identification information is provided can be interpolated by a signal synchronized with a series of immediately-preceding wobble signals.
Thus, the recording and/or reproducing timing signal obtained from the wobble signal is prevented from being deteriorated due to the identification signal of the identification information portion, and hence the position information from the wobble information can be highly reliably obtained even at the position located immediately after the identification information. Specifically, since the area located immediately after the identification information that cannot be detected can be accessed highly reliably, it is possible to maintain a reliability with which information can be recorded on and/or reproduced from the recording medium. Therefore, it becomes possible to carry out a real time recording and/or reproduction and a highly-reliable recording without the dropout of the information at all.